fix img tag linting errors

src/lib/components/Preview.svelte

@@ -207,7 +207,7 @@
 {#snippet coverImage(rootId: string, index: number, depth: number)}
   {#if hasCoverImage(rootId, index)}
     <div class="coverImage depth-{depth}">
-      <img src={hasCoverImage(rootId, index)} >
+      <img src={hasCoverImage(rootId, index)} alt={title} />
     </div>
   {/if}
 {/snippet}

src/lib/components/util/Details.svelte

@@ -20,7 +20,7 @@
 <div class="flex flex-row md:space-x-4 max-sm:flex-wrap">
   {#if image}
     <div class="flex col">
-      <img class="md:max-w-48 max-sm:w-full object-cover" src={image} />
+      <img class="md:max-w-48 max-sm:w-full object-cover" alt={title} src={image} />
     </div>
   {/if}
   <div class="flex flex-col col space-y-5  justify-center  align-middle">